The goal of Project 3 is to address key questions with respect to the role of mucosa-associated lymphoid tissues of the female reproductive tract (FRT) in HIV pathogenesis. Our overall hypothesis is that changes in the immune microenvironment of the FRT affect HIV disease progression. We will test this hypothesis in three specific aims. In Specific Aim 1, we will define the effects of aging on innate and adaptive cellmediated immune responses in blood and the female reproductive tract, and the potential impact of these effects on HIV pathogenesis and disease progression. Gender-based differences in immune function may be related to regulation by male and female sex hormones. Reproductive aging and menopause, characterized by a decline of estrogen levels, may affect function of estrogen-responsive immune cells, including T- and Blymphocytes and NK cells. We will test the hypothesis that reproductive aging alters cell-mediated immunity and the immune microenvironment of the FRT, potentially influencing HIV disease course. In Specific Aim 2, we will determine the effects of HIV infection on mucosal tissues of the female reproductive and gastrointestinal tracts in individuals at opposite ends of the disease spectrum, contrasting natural HIV controllers with off-treatment progressors. The majority of HIV transmission occurs via sexual contact across the mucosal surfaces of the cervix, vagina, and rectum. Although these tissues are key to HIV transmission and pathogenesis, studies of host-virus interactions at these sites have been limited. We hypothesize that the structural and functional changes in the reproductive mucosal tissues of HIVinfected women may parallel those observed in the Gl tract, in particular with respect to parameters such as CD4 memory subset depletion, immune activation, and regulatory T cells. In Specific Aim 3, we will define the effects of HIV infection on mucosal tissues of the FRT and the gastrointestinal tract in HAART recipients with low versus high recovery of blood CD4 cells. Individual responses to HAART vary significantly, and 10-30% of treated patients never reach the desired threshold of CD4 repopulation. We hypothesize that HAART-induced reconstitution of CD4 cells in the FRT may lag behind peripheral blood, paralleling the delayed reconstitution observed in the Gl tract. We will determine the effects of HIV infection on mucosal tissues of the FRT and the Gl tract in HAART recipients with low versus high recovery of blood CD4 cells. Taken together, these studies should provide many new insights into the role of the upper FRT in HIV pathogenesis. These studies are highly collaborative and will involve the Pis of Projects 1 and 2 as Co-Investigators or Collaborators.